1. Field of the Invention
The present invention generally relates to an antenna apparatus and a manufacturing method thereof, and particularly to a flat antenna apparatus using UWB (ultra-wide band) and a manufacturing method thereof.
2. Description of the Related Art
In recent years, radio communication technologies using UWB have attracted attention due to capability of radar positioning and communication with large capacity of transmission. Regarding the UWB, the FCC (federal communication commission) in the United States allowed the use of frequency bandwidth from 3.1 to 10.6 GHz in 2002.
The UWB is a communication method in which pulse signals are used in an ultra-wide band. Thus, an antenna used for the UWB is required to have a structure enabling transmission and reception of in the ultra-wide band.
An antenna made of a base board and a power feeder has been proposed as an antenna used in a bandwidth from 3.1 to 10.6 GHz allowed by the FCC (Non-patent Document 1)
FIGS. 1A and 1B show conventional antenna apparatuses. An antenna apparatus 10 shown in FIG. 1A includes a base board 11 and a power feeder 12 disposed thereon, the power feeder 12 having an inverted conical shape. The cone constituting the power feeder 12 is set such that a side face thereof forms an angle θ relative to an axis. In accordance with the angle θ, it is possible to obtain desired capability characteristics.
An antenna apparatus 20 shown in FIG. 1B includes the base board 11 and a teardrop-shaped power feeder 22 disposed thereon, the power feeder 22 being made of a cone 22a and a sphere 22b inscribed therein.
Non-patent Document 1: “An omnidirectional and low-VSWR antenna for the FCC-approved UWB frequency band” Takuya Taniguchi and Takehiko Kobayashi (Tokyo Denki University), The Institute of Electronics, Information and Communication Engineers, B-1-133, 2003, (presented on March 22, at room B201)
Patent Document 1: Japanese Laid-Open Patent Application No. 2000-196327
Conventional wide-band antenna apparatuses include a tabular base board and a power feeder having a conical or teardrop shape disposed thereon, so that such apparatuses are large in size and thin type antenna apparatuses have been desired.
FIGS. 2A and 2B show a UWB flat antenna apparatus 30 disclosed in the specification and the drawings of Japanese Patent Application No. 2006-91602 previously submitted by the inventors of the present invention. The UWB flat antenna apparatus 30 includes a dielectric base 31 having a top face 31a, on which an antenna element pattern 32, a strip line 33, and two ground patterns 34 and 35 are disposed, and a coaxial connector 50 mounted on an end of the base 31. In accordance with this, the apparatus is made to be smaller and thinner in comparison with conventional antenna apparatuses.
The strip line 33, the two ground patterns 34 and 35 on both sides of the strip line 33, and the base 31 constitute a coplanar microwave transmission line 40. The coaxial connector 50 is soldered and fixed to the strip line 33 and the ground patterns 34 and 35 at a terminal end of the coplanar microwave transmission line 40 extending from the antenna element pattern 32.
The UWB flat antenna apparatus 30 requires the dielectric base 31 and requires deposition steps and etching steps in order to form the antenna element pattern 32, the strip line 33, and the two ground patterns 34 and 35. Further, both deposition steps and etching steps require man-hours, so that it is difficult to reduce manufacturing costs thereof.